Interferons are cytokines, i.e. soluble proteins that transmit messages between cells and play an essential role in the immune system by helping to destroy microorganisms that cause infection and repairing any resulting damage. Interferons are naturally secreted by infected cells and were first identified in 1957. Their name is derived from the fact that they “interfere” with viral replication and production.
Interferons exhibit both antiviral and antiproliferative activity. On the basis of biochemical and immunological properties, the naturally-occurring human interferons are grouped into three major classes: Interferon-alpha (leukocyte), Interferon-beta (fibroblast) and interferon-gamma (immune). Alpha-interferon is currently approved in the United States and other countries for the treatment of hairy cell leukemia, venereal warts, Kaposi's Sarcoma (a cancer commonly afflicting patients suffering from Acquired Immune Deficiency Syndrome (AIDS)), and chronic non-A, non-B hepatitis.
Further, interferons (IFNs) are glycoproteins produced by the body in response to a viral infection. They inhibit the multiplication of viruses in protected cells. Consisting of a lower molecular weight protein, IFNs are remarkably non-specific in their action, i.e. IFN induced by one virus is effective against a broad range of other viruses. They are however species-specific, i.e. IFN produced by one species will only stimulate antiviral activity in cells of the same or a closely related species. IFNs were the first group of cytokines to be exploited for their potential anti-tumor and antiviral activities.
The three major IFNs are referred to as IFN-α, IFN-β and IFN-γ. Such main kinds of IFNs were initially classified according to their cells of origin (leukocyte, fibroblast or T cell). However, it became clear that several types might be produced by one cell. Hence leukocyte IFN is now called IFN-α, fibroblast IFN is IFN-β and T cell IFN is IFN-γ. There is also a fourth type of IFN, lymphoblastoid IFN, produced in the “Namalwa” cell line (derived from Burkit's lymphoma), which seems to produce a mixture of both leukocyte and fibroblast IFN.
The interferon unit or international unit for interferon (U or IU, for international unit) has been reported as a measure of IFN activity defined as the amount necessary to protect 50% of the cells against viral damage. The assay that may be used to measure bioactivity is the cytopathic effect inhibition assay as described (Rubinstein, et al. 1981; Familletti, P. C., et al., 1981). In this antiviral assay for interferon about 1 unit/ml of interferon is the quantity necessary to produce a cytopathic effect of 50%. The units are determined with respect to the international reference standard for Hu-IFN-beta provided by the National Institutes of Health (Pestka, S. 1986).
Every class of IFN contains several distinct types. IFN-β and IFN-γ are each the product of a single gene.
The proteins classified as IFNs-α are the most diverse group, containing about 15 types. There is a duster of IFN-α genes on chromosome 9, containing at least 23 members, of which 15 are active and transcribed. Mature IFNs-α are not glycosylated.
IFNs-α and IFN-β are all the same length (165 or 166 amino acids) with similar biological activities. IFNs-γ are 146 amino acids in length, and resemble the α and β classes less closely. Only IFNs-γ can activate macrophages or induce the maturation of killer T cells. These new types of therapeutic agents can are sometimes called biologic response modifiers (BRMs), because they have an effect on the response of the organism to the tumor, affecting recognition via immunomodulation.
Human fibroblast interferon (IFN-β) has antiviral activity and can also stimulate natural killer cells against neoplastic cells. It is a polypeptide of about 20,000 Da induced by viruses and double-stranded RNAS. From the nucleotide sequence of the gene for fibroblast interferon, cloned by recombinant DNA technology, (Derynk et al. 1980) deduced the complete amino acid sequence of the protein. It is 166 amino acid long.
Shepard et al. (1981) described a mutation at base 842 (Cys→Tyr at position 141) that abolished its anti-viral activity, and a variant clone with a deletion of nucleotides 1119-1121.
Mark et al. (1984) inserted an artificial mutation by replacing base 469 (T) with (A) causing an amino acid switch from Cys→Ser at position 17. The resulting IFN-β was reported to be as active as the “native” IFN-β and stable during long-term storage (−70° C.).
Rebif® (Serono—recombinant human interferon-β), the latest development in interferon therapy for multiple sclerosis (MS), is interferon(IFN)-beta-1a, produced from mammalian cell lines. Its recommended international Non-proprietary Name (INN) is “Interferon beta-1a”.
As with all protein-based pharmaceuticals, one major obstacle that must be overcome in the use of IFN-beta as a therapeutic agent, is the loss of pharmaceutical efficacy that can result from its instability in pharmaceutical formulations.
Physical instabilities that threaten polypeptide activity and efficacy in pharmaceutical formulations include denaturation and formation of soluble and insoluble aggregates, while chemical instabilities include hydrolysis, imide formation, oxidation, racemization, and deamidation. Some of these changes are known to lead to the loss or reduction of the pharmaceutical activity of the protein of interest. In other cases, the precise effects of these changes are unknown, but the resulting degradative products are still considered to be pharmaceutically unacceptable due to the potential for undesirable side effects.
The stabilization of polypeptides in pharmaceutical compositions remains an area in which trial and error plays a major role (reviewed by Wang (1999) Int. J. Pharm. 185:129-188; Wang and Hanson (1988) J. Parenteral Sci. Tech. 42:S3-S26). Excipients that are added to polypeptide pharmaceutical formulations to increase their stability include buffers, sugars, surfactants, amino acids, polyethylene glycols, and polymers, but the stabilizing effects of these chemical additives vary depending on the protein.
Cyclodextrins are cyclic oligosaccharides. The most common cydodextrins are alpha-cyclodextrin, which is composed of a ring of six glucose residues; beta-cyclodextrin, which is composed of a ring of seven glucose residues; and gamma-cyclodextrin, which is composed of a ring of eight glucose units. The inside cavity of a cyclodextrin is lipophilic, while the outside of the cyclodextrin is hydrophilic; this combination of properties has led to widespread study of the cyclodextrins, particularly in connection with pharmaceuticals, and many inclusion complexes have been reported. Beta-cyclodextrin has been of special interest because of its cavity size, but its relatively low aqueous solubility (about 1.8% w/v at 25° C.) and attendant nephrotoxicity have limited its use in the pharmaceutical field. Attempts to modify the properties of the natural cyclodextrins have resulted in the development of heptakis (2,6-dimethyl)-beta-cyclodextrin, heptakis (2,3,6-tri-O-methyl)-beta-cyclodextrin, hydroxypropyl-beta-cyclodextrin, beta-cyclodextrin-epichlorohydrin polymer and others. For a comprehensive review of cyclodextrins and their use in pharmaceutical research, see Pitha et at, in Controlled Drug Deliver, ed. S. D. Bruck, Vol. I, CRC Press, Boca Raton, Fla., pp. 125-148 (1983). For an even more recent overview, see Uekama et at, in CRC Critical Reviews in Therapeutic Drug Carrier Systems, Vol. 3 (1), 1-40 (1987); Uekama, in Topics in Pharmaceutical Sciences 1987, eds. D. D. Breimer and P. Speiser, Elsevier Science Publishers B. V. (Biomedical Division), 181-194 (1987); and Pagington, Chemistry in Britain, pp. 455-458 (May 1987). The use of cyclodextrins specifically in the field of peptide and protein delivery has bee reviewed by T. Ide et al in Adv. Drug Deliv. Rev, Vol 36, 101-123 (1999) and examples in the case of ovine growth hormone, interleukin 2 and bovine Insulin are described in Brewster et al., 1991, Phamaceutical Research, 8(6), 792-795.
WO 90/03784 and U.S. Pat. No. 5,997,856 describe a method for the solubilization and/or stabilization of polypeptides, especially proteins, by means of cyclodextrins. However no data on the stabilization if interferons are reported in this document.
U.S. Pat. No. 6,582,728 describes dry powder compositions for pulmonary administration containing interferon-beta also containing human serum albumin, which can further contain cyclodextrins. However, even in this case no data on the stabilization of interferon composition containing also cyclodextrins are reported in this document.
WO 2003/002152 described stabilized compositions comprising an interferon molecule and a specific derivative of cyclodextrin, i.e. sulfoalkyl ether cyclodextrin.
Consequently, there is a need for additional IFN-beta pharmaceutical compositions comprising physiologically compatible stabilizers that improve the solubility of this protein and stabilize the protein against aggregate formation, thereby enhancing their pharmaceutical utility.